In a 2 qt casserole dish, melt 1 stick of butter or margarine. Meanwhile, finely crush 1 tube of Ritz crackers. Add the crackers to the butter to form a crust. In a medium sized mixing bowl, add the following ingredients: 1 can cream of chicken soup, 1 8-oz carton of sour cream, 1 tablespoon poppy seeds, salt and pepper to taste, and 2 cups of diced cooked chicken. I usually poach 1 whole chicken and double the recipe or use leftover cooked chicken. Mix well. Pour into the casserole. Cook at 375 degree oven until hot and bubbly, approximately 25-30 minutes.